System for exchanging energy with a ground

ABSTRACT

A system for exchanging energy with a ground is disclosed. In at least one embodiment, it includes an elongate ground bore, a flexible sealing device for separating sections of the bore and extending inside and generally all along the bore and being closed at its ends, wherein the flexible sealing device, in use, is filled with a liquid whereby the flexible sealing device is pressed against walls of the bore. The system further includes at least a first duct, and heat recovery device, wherein said the at least a first duct is operatively connected to the heat recovery device and extends into the flexible sealing device. At least one sealing device is provided at the flexible sealing device at a predefined level along the bore, which at least one sealing device is adapted to seal at the level between the flexible sealing device and the bore.

FIELD OF THE INVENTION

The present invention relates to a system for exchanging energy with aground. It comprises an elongate ground bore, a flexible sealing devicefor separating sections of said bore and extending inside and generallyall along said bore and being closed at its ends, wherein said sealingdevice in use is filled with a liquid whereby said sealing device ispressed against walls of said bore. The system further comprises atleast a first duct, and heat recovery means, wherein said first ductextend from said heat recovery means into said sealing device.

BACKGROUND ART

Such systems for extracting energy from a ground are known. They areused to separate different levels in a borehole in the ground, i.a. inrocky grounds. Different layers at different levels in the ground oftenhave a inferior quality and may comprise not only different types ofrock, but also layers of sand or gravel of different fractions whichreduces the strength of the walls of the borehole. The borehole maycollapse or at least bring unwanted particles into the borehole with theground water that flows in the ground and especially in these in generalmore porous layers. If such a borehole is not sealed at least at thelevels of lesser quality the borehole may short-circuit the differentlevels via the hole. This may result in the water in the hole beingcontaminated or other holes being contaminated via these layers so thatundesirable effects occur, such as contamination or pressure drop. Forinstance, salt deposits at a depth of 100 m can easily contaminate awater well and make the water unfit for human use. An energy well isusually between 100 and 200 m deep. Often the ground water level is afew meters below ground level and above the ground water level the wellmust be reinforced with usually steel rings around the borehole sincethere is no pressure from the surrounding water to balance the pressurewithin the well.

A known such system for extracting energy from a ground is disclosed inthe applicants own patent application WO2006/126925. Other more usedsystems comprise the installation of sealing pipes within the boreholeat only the position of the layers of lesser quality. In such a systemthe positions of the layers are mo monitored during drilling of theborehole and thereafter these stiff pipes are installed and sealedagainst the walls of the borehole at the pipe ends. This latter systemrequires adjustments for each new well whereas the former system is amore straight forward method not in need of much on-site adjustments.

The bore hole is however still dependent on the quality of the rockaround the hole which determines whether the hole will be even andstraight or whether, for instance, the hole will be slightly larger thanintended since the surface of the hole has poor cohesion and will berough. In addition, harder or smoother kinds of rock enclosed in anotherwise uniform rock may result in the hole, when being drilled, notextending perfectly straight. Moreover the drill bit is gradually wornaway in use and will obtain a smaller diameter. This results in areduction of the diameter of the hole as well.

SUMMARY OF THE INVENTION

The object of the present invention is to further improve the sealing ofthe energy well and to preferably also reduce the costs for the completeinstalled energy well as well as preferably also reduce theenvironmental load of the completed installation.

This object is achieved by a system for exchanging energy with a ground,comprising an elongate ground bore, a flexible sealing device forseparating sections of said bore and extending inside and generally allalong said bore and being closed at its ends. The sealing device is inuse filled with a liquid whereby said sealing device is pressed againstwalls of said bore. The system further comprises at least a first ductand heat recovery means. The first duct is operatively connected to saidheat recovery means and extending into said sealing device. Sealingmeans are provided at said flexible sealing device at a predefined levelalong said bore, which sealing means are adapted to seal at said levelbetween said sealing device and said bore. Since the borehole iscompletely sealed off from the surrounding ground there will be noleakage and the liquid used for extracting the heat energy from theground comes in much better contact with the surrounding ground sincethe surface area towards the walls of the borehole is larger than thesurface area of the duct against the ground water of the traditionalopen borehole. The flexible sealing device is in itself advantageous totransport and install into the bore since it may be laid flat and rolledonto a storage and transportation device and also be installed in agenerally flat condition and not until after installation filled withliquid. Its inherent flexibility also easily adjusts to the walls of thebore and the often non-straight extension thereof. The sealing means areprovided to seal off vertical levels within the bore from one another inorder to minimize and preferably fully remove the leakage betweendifferent levels which otherwise may contaminate these or other levels.

In an embodiment said sealing means comprise a collar which is arrangedwithin said flexible sealing device at said predefined level, whichcollar is arranged and configured to exert a radial force against saidbore. Such a collar is improving the sealing off of different levelsalong the bore, on the outside of the sealing device, which the internalpressure within the sealing device may not always be able to. This maybe needed when the bore is rather uneven or there are levels along thebore of more water permeable material.

In an embodiment said collar is rigid and provided with material at itsouter periphery which expands in contact with said liquid. The rigidityof the collar is acting against the pressure exerted from the expandingmaterial so that the force is instead directed outwardly towards thesealing device and the bore to effect the intended seal.

In an embodiment the outer periphery of said rigid collar has a smallerdiameter than the inner diameter of said flexible sealing device inorder to certainly be possible to run down the bore.

In an embodiment the flexible sealing device comprises a tubular plasticfilm. This sealing device seals completely off the borehole from thesurrounding ground thus limiting the possibility for short circuitingany ground water between different layers at different depths within theborehole. This in turn leads to the possibility to install energy wellsin areas where it was not possible earlier. Furthermore, it is no longernecessary to monitor as thoroughly as before where these layers of morepenetrable ground materials are located in order to seal them. Also, thesealing system becomes less labour intensive thus cheaper.

In an embodiment is said tubular plastic film composed by at least twofilm layers. Hereby it is possible to determine the thickness needed inany borehole and to reduce the need for production and storage ofseveral thicknesses of the sealing device. For each energy well theground water conditions in combination with the type of grounddetermines the necessary thickness end the number of layers of film iscalculated or looked up in an here fore prepared table.

In an embodiment a second duct is operatively connected to said heatrecovery means and extending into said sealing device.

In an embodiment each first and second duct has a duct end which isopen, and in that the first duct end is located vertically below thesecond duct end. Since the sealing device is completely sealing off thesurrounding ground and liquid the ducts may be open in order to improvethe contact with the ground to improve the heat transfer.

In an embodiment said first duct end is located in a general bottomthird of said ground bore, and said second duct end is located in ageneral top third of said ground bore. The further to the top of thebore and to the bottom of the bore respectively each duct end ispositioned, the better the utilisation of the available heat energy ofthe energy well becomes.

In an embodiment said rigid collar is open for vertical flow of liquidin order to allow on open type of duct system to be used.

In one embodiment said first and second ducts are interconnected so asto form a continuous passage. This is a more traditional system, but maybe required i.a. when extra security requirements apply.

In an embodiment said rigid collar is closed for vertical flow of liquidwhich makes it even more rigid. An additional advantage with such acollar is that it may carry the weight of the water column verticallyabove it. Such a situation is La. advantageous when the level of groundwater surrounding the bore is rather deep into the ground. Under suchcircumstances the liquid pressure within the sealing device verticallyabove this ground water lever increases with the same amount of pressurecorresponding to the difference in height between the ground water leveland the liquid level. When placing a collar according to this embodimentwithin the sealing device, the collar can carry this additional pressureinstead of subjecting the sealing device to this additional pressure.

In an embodiment the sealing device at ground level has a mouth which isenclosed by a rigid tube of plastic material. In traditional systemssteel pipes are used which reinforce the ground around the sealingdevice if positioned in softer material than rock. According to thepresent invention the steel pipes may be used during drilling andinstallation of the system, but the steel pipes may be replaced by La.plastic tubes in order to reuse the steel tubes in other projects andthereby save costs and the environment by not using as much steel.

In an embodiment the sealing device at ground level has a mouth which isclosed by a sealing body.

In an embodiment said sealing body is secured between a top of saidrigid tube and said mouth of said sealing device.

In an embodiment said sealing body comprises a sealing ring secured tosaid top of said rigid tube, and a sealing lid, wherein said sealingdevice is clamped between said sealing ring and sealing lid.

In an embodiment said liquid is water which reduces the need foranti-freezing agents as is used in traditional systems which in turnlimit the environmental load and if a leak would accidentally happen,then there will only be water flowing into the surrounding ground.

In an embodiment said sealing device is made of non-rigid plastic whichmakes the sealing device adaptable to the shape of the borehole intowhich it is installed and any imperfections thereto, and further to makeit collapsible in order for it to be able to be rolled only a reel andminimising its transportation size.

In an embodiment said sealing device has a thickness of 0.2-1.5 mm. Inan embodiment said sealing device has a diameter which in usecorresponds substantially to the diameter of the bore.

In an embodiment said first and a second ducts each is made of non-rigidplastic, and preferably having a thickness of 0.2-1.5 mm. This makesalso the ducts' transportation size smaller and as such saves costs andimproves transportation efficiency.

In an embodiment said sealing means comprise a jacket enclosing saidsealing device. This improves the contact between the sealing device andthe walls of the bore since the jacket is able to adapt to and tosmoothen an uneven wall surface.

In an embodiment said jacket is provided generally at the same level assaid collar, which improves the seal.

In an embodiment said jacket is made of a material which expands incontact with water. After expansion the jacket may even fill gaps andimprove the seal.

In an embodiment said jacket is made of a rubber material, preferablybetween 25 and 45 ° Sh.

In an embodiment of the invention a system for extracting energy from aground is disclosed, comprising an elongate ground bore, a flexiblesealing device for separating sections of said bore and extending insideand generally all along said bore and being closed at its bottom end,wherein said sealing device in use is filled with a liquid whereby saidsealing device is pressed against walls of said bore, said systemfurther comprising a first and a second duct and heat recovery means,wherein said first and second ducts are operatively connected to saidheat recovery means and extending into said sealing device, wherein eachfirst and second duct has a duct end which is open, and which first ductend is located vertically below the second duct end. This embodiment maybe combined with any one or combinations of the above describedembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings which by way of example illustrate currentlypreferred embodiments of the present invention.

FIG. 1 is a cross-sectional view of an energy well with collector tubesprovided with a sealing device and a collar according to the presentinvention,

FIG. 1 b is a cross-sectional view of an energy well with an open systemof collector tubes provided with sealing device and two collarsaccording to the present invention,

FIG. 1 c is a plan view of a collar according to the present invention,FIGS. 2 a-2 b are cross-sectional views in sequence of the sealingagainst the surroundings at the mouth of the borehole,

FIG. 3 is a cross-sectional view of an energy well with collector tubesprovided with a multi-layered sealing device according to an alternativeembodiment of the present invention,

FIG. 4 a is a cross-sectional view of an energy well with a closedsystem of collector tubes provided with a sealing device and a collaraccording to the present invention

FIG. 4 b is a plan view of a collar according to an alternativeembodiment of the present invention,

FIG. 5 is a perspective and sectional view of an alternative embodimentof the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 a shows a sealing device 1 according to an embodiment of thepresent invention. The sealing device 1 is used in combination with anopen type of energy collecting system. It also illustrates the generallyvertical borehole 2 in rock 3. The borehole 2 is used as an energy wellfor extracting, for instance, heat for heating a house (not shown) orfor storing heat in the ground 3. In most cases the borehole 2 isnaturally filled with groundwater 4 while being bored. At the upperparts of the borehole 2 the rock 3 has ended and instead soil 3 is lyingon top of the rock 3 constituting the ground 3 or land 3. The rock 3 mayat some places penetrate the soil 3 and be visible, but it may also beas far down as hundreds of meters. Under normal conditions the rock 3may be found somewhere between a few up to ten to twenty metersunderneath the ground level. The present invention may be used under allof these conditions.

The sealing device 1 comprises a thin cylindrical one-layered “stocking”of non-rigid plastic, preferably a polyeten plastic and of approximately114 or 138 mm diameter and 0.4 mm thickness. The diameter of the sealingdevice 1 may be adjusted to the specific project, i.e. each borehole 2.Generally the bore 2 is drilled to a diameter of 114 mm and the diameterof the sealing device 1 is adapted to be lye flat against the wall ofthe bore 2 and to be flexible enough to follow its contours.

The sealing device 1 is at its bottom end sealed so that no water fromthe ground may penetrate into the inner parts thereof. The sealing ispreferably done by welding a continuous weld 60, but other known methodsmay be used, such as clamping between rigid plates, possibly togetherwith a material which expands in water 4 such as Hydrotight™, folding orby the use of tape. Below the weld 60 a protective cover (not shown) maybe slipped onto and surround the end of the sealing device 1 to protectit from the walls of the bore 2 when lowering it there into. To theprotective cover, or if no protective cover is used directly onto thesealing device 1 a weight 50 is connected to facilitate the lowering ofthe sealing device 1 into the bore 2. Both any protective cover and theweight 50 remains on the sealing device 1 after installation.

The length of the sealing device 1 is adjusted to extend substantiallyall the way up to the mouth of the bore 2 at the ground level. Thereason why it may sometimes be suitable not to let the sealing device 1open exactly at the level of the mouth of the bore 2 is that it may thenbe unlawfully manipulated or damaged. In these cases, a suitable levelof the opening of the sealing device 1 can be adjacent to the transitionbetween the frost level and the frost-free level, in Sweden about 1-2 mbelow ground level. That part of the hole which in that case ispositioned above the opening of the sealing device 1 but below the mouthof the bore 2 is sealed and can then be covered with, for instance,earth. See below for a detailed description of the sealing of thesealing device 1. It should be noted that normally all arrangements andfittings for a heat exchange system of the type according to the presentinvention is concealed under ground 3 in order to prohibit manipulationor weather influence. Hence, ducts 5, 6 normally bend at right angleinto a horizontal arrangement directly above seal 42.

The length of the sealing device 1 is also adjusted to extendsubstantially all the way down to the bottom of the bore, in Swedentypically some 100-200 meters from ground 3 level in order to utilisethe maximum capacity of the well. The bore 2 and consequently thesealing device 1 may be both shorter and longer due to the conditionsunder which the energy well is to be performing.

Between ground 3 level and the upper surface of the rock 3 possiblyanother few metres down in the borehole 2, steel pipes or in anembodiment of the invention plastic pipes, referred to as casings 40,are usually installed to shield the earth layers from the borehole 2.The vertically upper end of the casings 40 is sealed with a casing cover42 or seal 42 to confine any over-pressure inside the borehole 2 and toprevent the borehole 2 from being filled with soil and/or surface water.Connections to a heat pump in or connected to the house are thenarranged above the borehole 2 and the steel or plastic pipes 40.

As has been discussed above, there is in most cases soil above the rock3. Due to this soil, casings 40 are normally necessary to stabilise theshape of the bore 2. According to Swedish standards, this casing 40should extend at least 6 m below the upper edge of the rock to ensure atight transition. However, this does not always occur. According to thepresent invention, it is no longer necessary to have casings 40 6 m downin the rock, even if the standards may still stipulate this. The sealingdevice 1 in itself provides the security against leakage all the way upto the ground 3 level. Hence a casing 40 made of a plastic materialwhich is rigid enough to keep the bore 2 open may replace thetraditional steel pipes. During installation it may still be preferableto use a steel pipe casing 40, but this may after installation beremoved and be replaced by a plastic casing 40. This way the steelcasing 40 may be reused as a casing 40 in another project and a lot ofsteel material is saved which in turn saves costs and the environment.Often the steel pipes have a diameter of approx. 140 mm whereas the bore2 and the sealing device have diameters of preferably 114 mm, andconsequently the steel pipes are quite easily removed and replaced by a125 mm plastic pipe.

The sealing device 1 is suitably sealed at the mouth of the bore 2 inthe following way, see FIGS. 2 a-2 b. The seal 42 consists of two rigidsteel sheets 42 a and 42 c between which a thick rubber plate 42 b ismounted. The opening of the sealing device 1 is inserted between twometal rings 41 a and 41 b which are assembled with a screw 41 c. Themetal rings 41 a and 41 b have the same outer and inner diameter as thecasing 40 and can therefore be placed loosely on the upper edge of thecasing 41. The casing 40 may be the traditional steel pipes or theplastic pipes according to the present invention. When the metal rings41 a and 41 b together with the sealing device 1 are placed on thecasing 40, the seal 42 can be placed on top of the metal rings 41 a and41 b. In this position, parts of the rubber plate 42 b and the lowersteel sheet 42 c extend down into the casing 40 and the sealing device1. Through the entire seal 42 extend 4 through bolts 42 d which are nowtightened so that the lower steel sheet 42 c is pulled towards the uppersteel sheet 42 a, thus squeezing the rubber plate 42 b. The rubber plate42 b is now pressed towards the walls of the casing 40 and presses thesealing device 1 against the same so as to form a tight closure. As analternative to the illustrated embodiment the upper metal plate 42 a maynot protrude beyond the inner diameter of the casing 40 or even all theway out to the outer diameter of the casing 40. The pressure with whichthe bolts 42 d make the rubber plate 42 b expand to the sides to thecasing 40 is enough to keep the seal 42 intact also without this “upperlid” 42 a. The upper and lower plates 42 a and 42 c respectively do nothave to be made of metal, but any suitably rigid material or a suitablematerial in combination with a rigid design.

In order to extract heat energy from the energy well normally twocollector tubes 5, 6 are installed in the borehole 2, see FIG. 1 a.These collector tubes 5, 6 are one example of the first and second ducts5, 6 according to the claims. One tube supplies, in this case tube 5,and the other tube returns, in this case tube 6, the cooling mediumliquid 20 with which the tubes 5, 6 are filled. The supply tube 5 has anopen tube end which is positioned close to the bottom of the sealingdevice 1. The return tube 6 has an open tube end which is positionedeither at the seal 42 or penetrates down into the bore 2 only just ashort distance. In order to extract the maximum available heat energyfrom the borehole 2 the supply tube end should be positioned as far downthe bore 2 as possible and the return tube end as far up the bore 2 aspossible in order to maximise the distance there between. It is howeverreasonable to at least install the tube ends such that the return tubeend is positioned above the supply tube end to have the liquid 20circulating. The collector tubes 5, 6 are then connected to the heatpump system in or in close proximity of the house. The tubes 5, 6 arepreferably made of a rigid plastic material.

In order to extract energy from the well the liquid 20 may also bedriven in the reversed direction in comparison to the manner describedin the preceding paragraph if the energy removed from the ground 3 insuch a case is increased. The system may also be utilised to store heatin the ground or to cool the liquid 20 in a cooling system for buildingsor other applications. In these applications the liquid 20 may also bedriven either by supplying energy through the tube 5 ending at thegeneral bottom of the bore 2 and extracting at the general top of thebore 2, or in a reversed direction. Different ground 3 conditions mayaffect which is the best operational mode.

Returning to the embodiment of FIG. 1 a, when the heat pump circulatesthe liquid 20 in the system, the liquid 20 is entering into the wellthrough the supply tube 5 at the bottom of the well and the overpressure produced by the heat pump forces the liquid 20 up through thewell and into the return tube 6 which returns the liquid to the heatpump where the heat energy that the liquid 20 has absorbed within theenergy well is extracted and transferred to the heating system of thehouse. Since the sealing device 1 is completely sealed off from thesurrounding ground 3 there is no leakage of liquid 20 and the system isclosed off. However, within the system the collector tubes 5, 6 are openended in contrast to the traditional closed circuit the system accordingto the present invention may be defined as an “open” system.

The cooling medium liquid 20 consists traditionally of water and ananti-freezing agent, but according to the present invention it ispossible to use only water without the anti-freezing agent. This way noanti-freezing agent is needed and thus a reduced environmental loadingis achieved and a cut in costs results here from.

It is important for the liquid 20 of the collector tubes 5, 6 to makegood contact with the surrounding to function in a satisfactory mannerand be able extract energy to, for instance, the heat pump. Theinventive idea of the present invention is to make direct contact withthe surrounding ground 3 with the liquid 20 instead of as in thetraditional systems first have the liquid 20 (comprising water andanti-freezing agent) circulating in the closed collector tubes andextracting energy from the open bore 2 in which the ground watercirculates freely. According to the present invention the liquid 20comes in better contact with the surrounding and consequently the wellmay be more efficiently utilised and more energy may be extracted orsmaller well and system may be necessary for a specific need. Both maynaturally be achieved simultaneously.

In FIG. 1 a the collector tube 5 is also provided with a collar 70 whichencircles the tube 5. The collar is made of a polyethene material and isquite rigid. The vertical height of the collar 70 is preferably approx.5-15 cm high. The diameter of the outer periphery of the collar isslightly smaller than the bore 2 since the bore 2 not always iscompletely circular and may have walls that may sink in slightly due toless rigid material at certain levels and the collar 70 should bepossible to insert into the bore 2. On the outer periphery of the collar70 a continuous strip 71 of Hydrotight™ is applied, which is a materialthat expands in contact with water. The vertical height of the strip 71is preferably approx. 1-4 cm. Other materials having the same technicaleffect may be used as alternative. The expansion of the strip 71 inducesa force to be applied to the walls of the bore 2 in the range of up to90 kg/cm². This presses the sealing device 1 towards the wall and veryeffectively closes off any passage of water surrounding the sealingdevice 1 within the bore 2 from penetrating from one vertical levelwithin the bore 2 to another vertical level at the other side of thecollar 70. Due to the strong force applied by the expansion of the strip71 it is important that the collar is strong and rigid enough to alsocounteract against the force in order not to collapse. The strip 71 neednot be continuous along the periphery of the collar 70 if the materialis such that the expansion is directed so as to fill also the gapsbetween strip 71 parts or at least to make sure that the seal is tight.This type of seal may be needed when a level of a bore 2 has a porousstructure which may contaminate another level and thus make i.a. a waterwell useless due to salt leakage or other contaminants.

At the same level as the collar 70 on the outer periphery of the sealingdevice 1 it may be advantageous to even further improve the verticalseal by installing another strip 80 of a similar material as for strip71. Naturally also here other materials than Hydrotight™ may be used.When the sealing device 1 and collector tubes 5, 6 have been installedthe strips 71 and 80 will expand and together form a tight seal againstvertical leakage. The strip 80 is one embodiment of a sealing means 80according to the claims.

In FIG. 1 b a similar embodiment as in FIG. 1 a is illustrated, but itcan also be seen that a porous level within the bore 2 is closed orsealed off by the installation of two collars 70, one below and oneabove the level in question. The upper collar 70 makes sure that noleakage from an even higher vertical level is contaminating the level inquestion, or the other way around, and the lower collar 70 is in thesame manner prohibiting the contamination of the level in question orany lower porous level.

A difference between the present embodiment and the one illustrated inFIG. 1 a is that the sealing means 80 on the periphery of the sealingdevice 1 in the present case is not made of a material which expands incontact with water, but with an elastic material which adapts to therather rough surface of the bore 2 walls so that the sealing device 1seals off the vertical level from surrounding levels. Such an elasticjacket 80 may be made of a rubber material having a shore value ofapprox. 25-45 ° Sh. The jacket 80 may also be much higher in thevertical direction in comparison to the strip 80 of the FIG. 1a-embodiment. Preferably in the range of 0.5-1 m in the verticaldirection, but other lengths may apply. One reason for such a widesealing means 80 is that the tolerance level with which the collectortubes 5, 6 later are installed with may be much less. The thickness inthe horizontal direction may be in the range of approx. 0.5 to 3 cm. Thesealing means 80 in both this embodiment and the earlier one isinstalled on the sealing device 1 above ground and then lowered into thebore 2 together with the sealing device 1.

It should be noted that any number of collars 70, with or without anyembodiment of strips or jackets 80, may be installed according to theneeds of the specific bore 2 and ground 3 properties. It should also benoted that not only a one-layered sealing device 1 may be utilised, butseveral, if there is a need for instance due to security requirements.

In FIG. 1 c a collar or sealing means 70 according to one embodiment ofthe present invention is illustrated. There is an outer ring intended toprovide the stability and rigidity of the collar 70 which is the mainpart. In order to be able to fasten the collar 70 to the collector tubes5, 6 a generally centrically positioned ring 73 is provided and arms 74for carrying the outer ring on the inner ring 73. Since the presentinvention is an open type of energy well in which the two collectortubes 5, 6 communicate via the sealing device 1 and the ends of saidtubes 5, 6 most likely are positioned one on each side of the collar 70,the collar 70 need to provide for a vertical flow of liquid 20 and hencevertical through holes 72 are provided, in this case four. The strip 71is fastened by a glue or by using press-fit, for instance by the aid ofan O-ring or a expanding material which is arranged around the duct 5,6, on the outer ring of the collar 70 in an enclosure which is best seenin FIG. 1 a and 1 b. Also other manners of fastening of the strip 71 maybe utilised.

FIG. 3 discloses a further embodiment of the present invention in whichthe sealing device 1 comprises 3 concentrically positioned, i.e. onewithin the other, flexible sealing devices 1. The aim is to improve thesecurity of the system as a whole. If for instance the bore 2 isreaching a level where the wall of the bore 2 is made up of gravel andsmaller loose stones instead of the hard rock 2, the bore 2 wall may beless stiff and the diameter of the bore 2 may be slightly increased. Atthat level the wall of the bore 2 will not be an efficient wall againstwhich the sealing device 1 may rest, but instead the sealing device 1may need to be self supportive. Unless the wall of the sealing device 1is strong enough in itself the sealing device 1 may rupture and thesealing effect is lost and the system and the surrounding environmentare adversely affected.

Another reason for installing several layers to build up the sealingdevice 1 is that if the ground water level is rather deep into theground the seal 42 is generally still installed at ground level orslightly below that, which means above ground water level. However, thisintroduces a higher internal pressure within the sealing device 1towards its bottom, and a further risk is introduced if the walls of thebore 2 are not strong enough to withstand this internal pressure.

The reason for not producing and installing a thicker sealing device 1rather than installing several layers is amongst other things that it issimpler and cheaper to only produce one thickness rather than several.Furthermore, the effect of collapsing the sealing device 2 and rollingit onto a reel for transportation purposes is less pronounced or evenlost.

A suitable thickness of the sealing device 1 may vary between 0.5 and1.5 mm, but deviations may be necessary due to the circumstances, bothto smaller and greater thicknesses. The sealing device 1 may bemanufactured and delivered as a continuous “stocking” with a certaindiameter, which is cut by the fitter to a suitable length when theborehole 2 is completed. Alternatively the sealing device can becompleted in the factory. The diameter of the sealing device 1 issuitably selected to substantially correspond to the diameter of theborehole 2, thus fitting tightly against the same. When installingseveral concentrically positioned layers of the sealing device 1 theinner layers may be produced with a diameter corresponding to the innerdiameter of the surrounding layer.

In this embodiment a collar 70 is installed having a strip 71 to sealoff the different levels within the bore 2. However in this embodimentit has been determined that no strip 80 on the outer surface orperiphery of the sealing device 1 has been necessary.

The sealing device 1 is installed in the borehole 2 by first sealing theend by applying a preferably continuous weld 60 and either fold the endas is disclosed in FIG. 1 a and described below, or by fastening theprotective cover or some other suitable protection, to which the weight50 is then connected.

The sealing device 1 may be closed at its end facing the bottom of thebore 2, FIG. 1 a II, by first having its open end being folded along theentire width of the sealing device 1, thus forming a triangular tab atan angle of 45° to its longitudinal extent. Subsequently the now foldededge is folded once in the opposite direction, FIG. 1 a III, thusforming a triangular tab at an angle of 45° to the longitudinal extentof the sealing device 1, the tip of the triangular tab being formedalong the centre line of the sealing device 1 seen in its longitudinalextent, FIG. 1 a IV. A small through hole is made through thistriangular tab and provided with a reinforcing ring in the form of astaple, FIG. 1 a V. A cotter pin can then be passed through this staple,thus holding the sealing device 1 attached to its weight 50. Finally oneor more lines 60 are welded across the sealing device 1 just above thejust formed fold lines, said welds 60 ensuring that the sealing device 1is perfectly sealed at this end.

The weight 50 helps the sealing device 1 to be dragged down to its endposition. If further layers of the sealing device 1 should be installed,the same procedure to seal and install them is followed until a suitablenumber of layers are installed. The total length of the bore 2 must beadapted to the number or layers of the sealing device 1, since eachlayer normally is provided with its on set of weld 60, protective coverand weight 50 which adds to the total length of installed sealing device1.

When the sealing device 1 is installed it is filled with water 20,either from above or, as shown in FIG. 3, using a tube 30 inside thesealing device 1. After that the collector tubes 5, 6 are let down intothe bore 2 each to its own position inside the sealing device 1, and theseal 42 is connected to the mouth.

As a rule of thumb there are two types of boreholes 2: those naturallyfilled with water and those not filled and thus being empty. The holes 2which from the beginning are filled with water can apply a waterpressure to the installed collector tubes 5, 6 and the sealing device 1so that a water pressure inside the sealing device 1 may have to bebuilt up to expand the sealing device 1 against the borehole 2 wall.This is conveniently done by passing, together with the collector tubes5, 6 and the sealing device 1 while being installed, a water tube downin the bore 2, see FIG. 3. The water tube 30 is arranged beside thecollector tubes 5, 6 and inside the sealing device 1. The water tube 30has one opening adjacent to the tight-fitting connection of the sealingdevice 1 to or under the collector tubes 5, 6 and its other openingabove the ground to be connected to a suitable pump system. With theseparts installed in the borehole 2, water 20 is pumped down in thesealing device 1 through the water tube 30, this water 20 thus pressingaway any other water in the bore 2, so that the sealing device 1 placesitself along the side of the borehole 2 wall. In this way, differentlevels in the borehole 2 are sealed, thus preventing groundwater fromone level in the hole from reaching another level. Also no specialsealing is required of that part (in most cases the upper part) of thehole 2 that does not consist of rock but of earth and/or clay, whichotherwise would normally have been sealed by means of, for instancesteel rings, referred to as casings 40. Thus this sealing device 1 makesit possible to utilise the entire borehole 2 for energy withdrawal allthe way from its bottom to its opening at the ground level. Anotheradvantage is that no surface water from the ground surface can flow downin the borehole 2 since the sealing device 1 is suitably sealed againstthe environment at the ground level.

After installation and filling the sealing device 1 with water 20, thesystem is ready to be connected to a suitable heat pump in a house andthereafter the energy well is ready for use. It is possible for thewater tube to remain in the borehole 2 since further filling with watermay be required at a later stage. This water tube can also be used if itappears necessary to maintain a certain overpressure inside the sealingdevice 1. By mounting a pressure-sensitive transducer on the water tubeand connecting the transducer to a reading system, it will be possibleto continuously read the condition of the borehole 2. This informationcan be sent in prior-art manner either wirelessly or by appropriatewiring to a reading position, for instance, in connection with theinstallation for withdrawal of energy from the energy well.

In a borehole 2 which is empty from the beginning, or if the waterpressure in the borehole is so low that it does not prevent the sealingdevice 1 from being filled with water 20 without overpressure, it ispossible to fill the sealing device 1 without water pressure frominside. Thus in this case it is not necessary, but still possible, touse a water tube 30 according to the above method. Instead collectortubes 5, 6 and a sealing device 1 can be inserted and installed in thehole 2 as described above, after which water 20 can be supplied throughthe opening of the sealing device 1 at the ground level. Even if a watertube 30 has not been used in this case for supplying water 20, apressure-sensitive transducer can still be inserted into the upper partof the borehole to monitor its condition.

It should be noted that the open type of system according to the abovedescribed embodiments may well be used without the use of collars 70 orjacket 80 if the ground 3 and bore 2 so allows. This may be the casewhen the bore 2 has appropriately even walls and/or the internalpressure of liquid 20 within the sealing device 1 is enough to sealagainst the bore 2 walls between different levels therein.

Yet another embodiment of the present invention is illustrated in FIG. 4a. In this embodiment a closed type of system is used in which the twocollector tubes 5, 6 are interconnected at the bottom of the sealingdevice 1. The forward end of the collector tubes 5, 6 is then preferablyprovided with its own weight 51 connected via a connector 53 to aprotective cover 52 which are useful during installation. The collar 70with strip 71 may in this case also be used to better seal off verticallevels outside of the sealing device 1. Also a jacket 80 may be used ofany kind as already discussed. Such a jacket 80 is however not used inthe embodiment as illustrated. In FIG. 4 b a collar 70 is illustratedwhich is provided with two holes 73′ and 73″ to connect to both ducts 5,6. In this embodiment the collar 70 is not open, i.e. having a closedwall 74, for vertical flow of liquid 20 which is possible when thecollector tubes 5, 6 are a closed system. Also an open collar 70 withopenings 72 may be used

In a further embodiment of the present invention which is illustrated inFIG. 5 a sealing device 1 is used which is provided with a collar 70 andstrip 71 (and possibly a jacket 80), but in which the sealing device 1is not extending all the way down the bore 2. In this embodiment asealing means is used to seal off the sealing device 1 at its bottom endfrom the rest of the bore 2. Other embodiments having one or severallonger or shorter sealing devices 1 along all or parts of the bore 2 mayalso be contemplated due to the particulars of each bore 2.

In a further embodiment of the present invention the jacket 80 may bedesigned as a carrier 80 e.g. in the form of a plastic or rubber thinsheet which is e.g. glued or taped to the outer periphery of the sealingdevice 1 at a predefined level before installation. In this embodimentthe jacket 80 could be used with or without a collar or sealing means 70within the sealing device 1. The outer diameter of this carrier islarger than the diameter of the bore 2 so that the carrier 80 afterinstallation becomes at least slightly cup-shaped and bears against thebore 2 walls. After installation of the sealing device 1 a sealingmaterial e.g. montmorillonite or other clay material is poured into thebore 2 on the outside of the sealing device 1. The sealing materialfalls down and is caught up by the carrier 80 and a layer of sealingmaterial is built up. The amount of sealing material is adapted to eachspecific bore 2 so that a vertical seal of the bore 2 is achieved, atleast when liquid 20 is expanding the sealing device 1. This type ofsealing means 80 or jacket 80 may also be utilised all the way from thebottom of the bore 2 up to a desired level. Then there is no need for acarrier, since the bore 2 bottom carries the weight of the claymaterial. If needed, a carrier 80 and clay material may be installedvertically above this desired level so that there is no jacket 80 alonga part of the bore 2. Any number of sealing means 70, 80 may beinstalled along the bore 2, of any combination of embodiments hereinaccording to the needs of the specific bore 2.

The above disclosed embodiments of the present invention representmerely a minor range of contemplated embodiments. There are a widevariety of embodiments within the scope of the claims that may beutilised to adapt the system to the current conditions. Some embodimentsmay i.a. be:

The sealing means 70 as discussed in the more general sense may also bee.g. a flat and rather thick rubber plate which is forced onto the ductor ducts 5, 6 and which has an outer diameter which is slightly largerthan the diameter of the bore so that the inherent elasticity of therubber material is exerting a force outwardly against the bore 2 wallsand hence provides for a seal between the bore 2 and the sealing device1. This type of sealing means 70 is also closed for vertical flow ofliquid 20 within the sealing device 1 and will consequently also carrythe weight of the liquid 20 vertically above the collar 70 or sealingmeans 70. Another contemplated embodiment of this type is a more thinplate of plastic or otherwise flexible material which also has an outerdiameter larger than the bore 2, but which is utilising the inherentflexibility of the total design to exert the outwardly directed force byflexing or bending the plate outer periphery into a cup-shape afterinstallation.

Sealing means 70 of the type described in the previous paragraph may beused, at least in combination with a closed loop duct system, incombination with a clay material, cement material or other suitablematerial in order to withstand any compressive forces from thesurrounding ground 3 if the bore 2 walls are not rigid enough to keepthem selves intact, or if the liquid 20 pressure within the sealingdevice 1 is not sufficient to withstand such forces. The sealing means70 is then installed at the appropriate level and such material ispoured on top. Several such sealing means 70 with such material may beused in one bore 2. Such material may also be used in order to close theend of the sealing device 1 at the general bottom of the bore 2, or asdescribed above, to keep the bore 2 intact at this level. Thisembodiment may naturally also be used with or without a jacket 80.

The bore 2 needs not be circular, but may have any shape. This alsoapplies to the shape of the ducts 5, 6 and the collar 70. However, inthat case the sealing device 1 may need to be adjusted in shape to theintended use. If either the hole 2 or the ducts 5, 6 or the collar 70 isin the shape of a polygon, for instance a hexagon, a circular sealingdevice 1 may yet function, provided that either the material of thesealing device 1 is sufficiently weak (“non-rigid”) or the constructionof the sealing device 1 is sufficiently flexible.

The multi-layered sealing device 1 may be delivered to the installationsite not merely as a long circular but flattened plastic film which iscut to length and installed one layer after the other, but the sealingdevice 1 may already at the production plant be assembled in themulti-layer build up, and the sealing weld 60 and the protective cover52 and weight 50 may also be connected in advance. The volume betweentwo concentric sealing films in such a multi-layer device 1 may beutilised as one of the ducts 5, 6 for removing or inserting energy fromthe ground 3. In this case the inner film is smaller in diameter thanthe outer film in order to provide such duct 5, 6 space.

The sealing device 1 may not only be a “hose” of flat sheet plastic, butmay be built up by small capillary stems or pipes along the outerperiphery, either alone or in combination with a flat sheet. Thesecapillary stems or pipes may be utilised as one of the ducts 5, 6 forextracting or inserting energy from the ground 3.

The system may according to an embodiment of the invention utilise morethan one borehole 2 and have several boreholes 2 interconnected in orderto extract more energy with the same heat pump. Naturally the borehole 2may have a different diameter and length, in particular when installingseveral interconnected ones. Also an elongate bore 2, i.e. which has anextension both in the vertical and in the horizontal direction, may beutilised having several loops of ducts 5, 6. Also, the collar 70 maythen be adapted to the cross-section of the bore 2 and extend in asimilar manner along the bore 2. Under any circumstances the collar 70may also be utilised as carrier for the ducts 5, 6 in order to keep themin place at appropriate distances.

The collector tubes 5, 6 may as well as the sealing device 1 be made ofa flexible material in order to enable the same positive effect ofrolling on a reel during transportation in order to minimise thetransported volume. Such an embodiment may be of rather thin thickness,in the same range as for the sealing device 1.

The metal rings 41 a and 41 b of the seal 42 may naturally be of anothersuitably rigid and durable material such as a plastic.

The energy well may not only be located in rocky grounds 3, but also inother types of grounds 3 such as sand or clay. The borehole 2 is thengenerally achieved by producing a so called “standing hole” by pressingaway the ground material and reinforcing it with e.g. montmorillonite orother clay material. The function of the bore 2 after reinforcementbecomes the same as in rocky grounds and hence the system and thesealing device 1 are installed in a similar manner. Another ground 3type comprises one or several aquifers. The system according to any oneof the embodiments of this application may be utilised also if a bore 2passes such aquifers since the liquid 20 pressure within the sealingdevice 1 is keeping the system expanded also in water and the sealingdevice 1 possibly in combination with any sealing means 70, 80 isensuring the integrity of the system. Such an aquifer could be utilisedas a storage facility for ground energy by installing two bore holes 2,one at either side of the aquifer. In each bore 2 a system according tothe invention is installed and in one of the systems energy is insertedinto the water of the aquifer, and in the other energy is extracted. Inthis way a heat exchanger is created.

The system may be utilised in a slanted manner or in a curved manner,and even installed into a first bore 2 in connection with a second bore2 such that said sealing device 1 interconnects said two bores 2 andforms one continuous system for energy exchange.

1. A system for exchanging energy with a ground, comprising, an elongate ground bore; a flexible sealing device for separating sections of said bore and extending inside and generally all along said bore and being closed at its ends, wherein said flexible sealing device, in use is filled with a liquid whereby said flexible sealing device is pressed against walls of said bore; at least a first duct; heat recovery device, wherein said first duct is operatively connected to said heat recovery device and extending into said sealing device; and at least one sealing device provided at said flexible sealing device at a predefined level along said bore adapted to seal at said level between said flexible sealing device and said bore.
 2. A system for extracting energy according to claim 1, wherein said at least one sealing device comprises a collar, arranged within said flexible sealing device at said predefined level, the collar further being arranged and configured to exert a radial force against said bore.
 3. A system for extracting energy according to claim 2, wherein said collar is rigid and provided with material at its outer periphery which expands in contact with said liquid.
 4. A system for extracting energy according to claim 3, wherein the outer periphery of said rigid collar has includes a smaller diameter than the inner diameter of said flexible sealing device.
 5. A system for extracting energy according to claims 1, wherein said flexible sealing device (1) comprises a tubular plastic film.
 6. A system for extracting energy according to claim 5, wherein said tubular plastic film is composed of at least two film layers.
 7. A system for extracting energy according to claims 1, further comprising a second duct operatively connected to said heat recovery device and extending into said flexible sealing device.
 8. A system for extracting energy according to claims 1, wherein said at least a first duct includes a first and second duct each including a duct end which is open, the duct end of the first duct being located vertically below the duct end of the second duct.
 9. A system for extracting energy according to claim 8, wherein said first duct end is located in a general bottom third of said ground bore, and said second duct end is located in a general top third of said ground bore.
 10. A system for extracting energy according to claim 8, wherein said rigid collar is open for vertical flow of liquid.
 11. A system for extracting energy according to claim 1, wherein said at least a first duct includes a first and second duct, the first and second ducts being interconnected so as to form a continuous passage.
 12. A system for extracting energy according to claim 11, wherein said rigid collar is closed for vertical flow of liquid.
 13. A system for extracting energy according to claim 1, wherein the sealing device, at ground level, includes a mouth which is enclosed by a rigid tube of plastic material.
 14. A system for extracting energy according to claim 12, wherein the flexible sealing device, at ground level, includes a mouth which is closed by a sealing body.
 15. A system for extracting energy according to claim 14, wherein said sealing body is secured between a top of said rigid tube and said mouth of said flexible sealing device.
 16. A system for extracting energy according to claim 15, wherein said sealing body comprises a sealing ring secured to said top of said rigid tube, and a sealing lid, wherein said flexible sealing device is clamped between said sealing ring and sealing lid.
 17. A system for extracting energy according to claim 1, wherein said liquid is water.
 18. A system for extracting energy according to claim 1, wherein said flexible sealing device is made of non-rigid plastic.
 19. A system for extracting energy according to claim 1, wherein said flexible sealing device includes a thickness of 0.2-1.5 mm.
 20. A system for extracting energy according to claim 1, wherein said flexible sealing device includes a diameter which, in use corresponds substantially to the diameter of the bore.
 21. A system for extracting energy according to claim 1, wherein said first and a second ducts each is made of non-rigid plastic,
 22. A system for extracting energy according to claim 1, wherein said at least one sealing device comprises a jacket enclosing said flexible sealing device.
 23. A system for extracting energy according to claim 22, wherein said at least one sealing device comprises a collar, arranged within said flexible sealing device at said predefined level, the collar further being arranged and configured to exert a radial force against said bore and wherein said jacket is provided generally at the same level as said collar.
 24. A system for extracting energy according to claim 22, wherein said jacket is made of a material which expands in contact with water.
 25. A system for extracting energy according to claim 22, wherein said jacket is made of a rubber material.
 26. A system for extracting energy from a ground, comprising, an elongate ground bore; a flexible sealing device for separating sections of said bore and extending inside and generally all along said bore and being closed at its bottom end, wherein said flexible sealing device, in use is filled with a liquid whereby said flexible sealing device is pressed against walls of said bore; a first and a second duct; and heat recovery device, wherein said first and second ducts are operatively connected to said heat recovery device and extending into said flexible sealing device, wherein each first and second duct has a duct end which is open, and wherein a duct end of the first duct is located vertically below the duct end of the second duct.
 27. A system for extracting energy according to claim 9, wherein said rigid collar is open for vertical flow of liquid.
 28. A system for extracting energy according to claim 1, wherein the sealing device, at ground level, includes a mouth which is closed by a sealing body.
 29. A system for extracting energy according to claim 21, wherein said first and a second ducts each is made of non-rigid plastic having a thickness of 0.2-1.5 mm.
 30. A system for extracting energy according to claim 25, wherein said jacket is made of a rubber material between 25 and 45 ° Sh. 